Fastener unit

ABSTRACT

The present invention relates generally to fastener units of the type comprising pre-assembled screw and washer members, and more particularly to fastener units in which the washer element is free from direct contact with the screw member. The fastener unit disclosed herein comprises a screw member having a threaded shank extending from the clamping side of a screw head and a generally tubular washer retainer member encircling and peripherally impinging the screw shank in the vicinity of the clamping surface of the screw head. An apertured washer member encircles the tubular member provides shoulder means beneath the washer to prevent unauthorized separation of the washer and screw member.

Elmted States Patent 1 1 3,687,184

Wagner 1 1 Aug. 29, 1972 [54] FASTENER UNIT FOREIGN PATENTS ORAPPLICATIONS 2] Inventor: David g Elmhurst, Ill. 1,109,551 9/1955 France..85/1 JP Assigneez Illinois works Inc. C icago, Natherlands PrimaryExaminer-Marion Parsons, Jr.

[22] Filed: Dec. 30, 1969 Att0mey-Olson, Trexler, Wolters & Bushnell.Robert Appl. No.: 889,154

W. Beart, Michael Kovac, Barry L. Clark and Jack R. Halvorsen [5 7]ABSTRACT The present invention relates generally to fastener units ofthe type comprising pre-assembled screw and washer members, and moreparticularly to fastener units in which the washer element is free fromdirect contact with the screw member. The fastener unit disclosed hereincomprises a screw member having a threaded shank extending from theclamping side of a screw head and a generally tubular washer retainermember encircling and peripherally impinging the screw shank in thevicinity of the clamping surface of the screw head. An apertured washermember encircles the tubular member provides shoulder means beneath thewasher to prevent unauthorized separation of the washer and screwmember.

7 Claims, 5 Drawing Figures PATENTEDAus 29 I972 JVWM WWW w FASTENER UNITThe present invention is concerned primarily with the association ofnovel washer retainer means with a fastener unit comprising a washertelescopically associated with a screw shank.

More specifically, the present invention contemplates the provision ofan improved fastener unit construction wherein a washer may be securedagainst axial displacement with respect to a screw shank by auxiliaryretainer means of novel and inexpensive design.

It is a further object of the present invention to provide a fastenerunit of the type referred to above wherein improved washer retainingmeans is provided which will electrically insulate the washer from anassociated screw member.

More specifically, the present invention contemplates an improvedpre-assembled washer and screw device wherein the washer is soconstructed that it will yield axially when clamped against a worksurface, thereby increasing the impingement of the inner margin of thewasher against the peripheral surface of a washer retainer member.

The foregoing and other objects and advantages will be more apparentfrom the following detailed description when considered in connectionwith the accompanying drawing wherein:

FIG. 1 is a side elevational view of a fastener unit of the typecontemplated hereby;

FIG. 2 is an enlarged fragmentary central sectional view takensubstantially along the line 22 of FIG. 1;

FIG. 3 is a plan view of the device shown in FIG. 1;

FIG. 4 is an enlarged vertical sectional view similar to FIG. 2disclosing the washer element finally tightened against the worksurface; and

FIG. 5 is an enlarged fragmentary sectional view of the electricallynon-conductive washer retainer member.

Referring now to the drawing more in detail, wherein like numerals havebeen employed designates similar parts throughout the various figures,it will be seen that one embodiment of the invention comprises afastener unit designated generally by the numeral 10. The fastener unitincludes a screw member 12 and a washer member 14. The screw member 12is provided with a threaded shank 16 extending from and formed integralwith a head 18. The underside of the head 18 provides a clamping surface20 and in the disclosed embodiment, the washer 14 has an annular bodyportion 22 of substantially conical form. The outer margin of the washer14 is provided with suitable teeth 24 adapted for aggressive impingementwith the surface of a workpiece 26 as shown in FIG. 4.

Attention is now directed to a generally tubular washer retainer memberdesignated generally by the numeral 28. The retainer member 28 ispreferably formed of electrically non-conductive material and includes asleeve portion 30 terminating at its upper extremity in a radial flange32. Axially spaced from the flange 32 is an annular shoulder 34 whichdefines an outer periphery having a diameter which is sufficientlylarger than the internal diameter of the washer 14 so as to prevent thewasher from being unintentionally separated from the screw member 12.Before the washer 14 is tightened against the work surface as shown inFIG. 4, the diameter of the inner periphery of the sleeve 30 in thevicinity of the flange 32 is preferably slightly larger than the maximumexternal diameter of the screw shank. This is clearly illustrated inFIG. 2.

In assembling the parts, the retainer member 28 is first telescopicallyassociated with the washer 14, and this assembly is then telescopicallyassociated with the threaded shank 16 of the screw member 12. The innerdiameter of the sleeve adjacent the free extremity thereof is normallyslightly smaller than the maximum outer diameter of the screw shank.Hence the sleeve 30 must be forced over the threads of the shank and itis this impingement of the sleeve 30 with the outer periphery of thescrew shank which prevents unauthorized or unintentional axialdisplacement of the sleeve with respect to the threaded shank. Theshoulder 34 of the retainer member 28 cooperates to prevent dislodgementof the washer 14.

In practice, the workpiece will generally comprise two layers 26 and26'. One of these layers 26 or 26 being of non-conductive material. Inthis environment, the washer retainer 28 will effectively electricallyinsulate the washer 14 from the screw member 12. The desired insulationalso will result if a nonconductive insulating sheet (not shown) wereplaced between workpiece 26 and 26'.

As the screw is tightened in the workpiece 26 and the washer 14 issubjected to axial clamping forces, said washer will have a tendency toflatten and thereby cause reduction in the normal diameter of the washeraperture resulting in aggressive impingement of the washer margin withthe outer periphery of the sleeve 30 as shown in FIG. 4. The innermargin of the washer is preferably reduced in the thickness to enhancethe aggressiveness with which said margin will engage, and in fact,imbed itself within the retainer periphery.

From the foregoing it will be apparent that the present inventioncontemplates a very simple, yet practical three piece fastener unitcomprising a screw member, a washer member and an electricallynonconductive or sealing type washer retainer member. Fastener unitshave heretofore been available which depend upon an extruded threadconvolution for securing a washer against dislodgement. Such fastenerunits require that the washer be first telescopically associated with ascrew blank and the thread convolutions thereafter rolled upon the bank.The present invention makes it possible for a washer to betelescopically associated with a screw member upon which the threadshave previously been rolled. The simple plastic retainer is veryinexpensive to produce and greatly facilitates the ease with which thethree parts may be brought together as an assembled unit.

I claim:

1. A fastener unit including a screw member having a threaded shank, ahead at one extremity thereof having a clamping surface from which theshank extends, a generally tubular washer retainer member encirclingsaid shank portion in the vicinity of said head, said retainer memberbeing made of a dielectric material and having an integral radial flangeof substantial radial extent positioned adjacent to and traversing saidclamping surface, an apertured dished washer member telescopicallyassociated with said tubular retainer member oriented with its convexsurface adjacent the flange of the retainer member and positionedadjacent to the underside of said flange means, and externallyprojecting shoulder means formed in the tubular member at a positionspaced axially from said flange means, the outer periphery defined bysaid shoulder means being greater in diameter than said washer aperturewhereby to prevent unauthorized axial separation of the washer and saidretainer member, said washer retainer member at a position spacedaxially from said flange means formed inwardly to present a diametermeasurement less than the crest diameter of the threads of said screwmember, said inwardly formed portions being laterally yieldable topermit telescopic association with said screw member, said tubularretainer member after being mounted on said screw member being laterallyyieldable to permit telescopic association of the apertured washerwhereby to provide an electrically insulated washer relative to thescrew member with which it is associated.

2. A fastener unit as set forth in claim 1, wherein the shoulder meanscomprises a radially outwardly deflected annular portion of said tubularretainer member.

3. A fastener unit as set forth in claim 1, wherein the tubular retainermember has an internal diameter which progressively decreases toward theentering extremity of the screw member associated therewith.

4. A fastener unit as set forth in claim 1, wherein the screw member hasan unthreaded shank portion adjacent the clamping surface of the head.

5. A fastener unit as set forth in claim 1, wherein the inner margin ofthe washer member defining the washer aperture is of substantiallyreduced axial thickness.

6. A fastener unit as set forth in claim 1, wherein the inner margin ofthe washer member defining the washer aperture progressively diminishesradially inwardly to provide a marginal edge for engaging the outerperiphery of the tubular retainer member.

7. A fastener unit as set forth in claim 1, wherein the outer margin ofsaid washer member being provided with teeth for aggressively impingingsaid work surface.

UNITED STATES PATENT oFFlcE CERTIFICATE OF CORRECTIUN Patent No. 3 ,687,184 Dated August 29, 1972 Inventor(s) David P. Wagner It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

In the abstract, line 12, after "member" insert on the underside ofintegral flange and tubular member-- Col. 2 line 50, change "bank" to-blank-- Signed and sealed this 24th day of April 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents CRM PO-105O (10-69) USCOMM'DC 60376-P59 Q U.S. GOVERNMENTPRINTING OFFICE: I959 0-366-334

1. A fastener unit including a screw member having a threaded shank, ahead at one extremity thereof having a clamping surface from which theshank extends, a generally tubular washer retainer member encirclingsaid shank portion in the vicinity of said head, said retainer memberbeing made of a dielectric material and having an integral radial flangeof substantial radial extent positioned adjacent to and traversing saidclamping surface, an apertured dished washer Member telescopicallyassociated with said tubular retainer member oriented with its convexsurface adjacent the flange of the retainer member and positionedadjacent to the underside of said flange means, and externallyprojecting shoulder means formed in the tubular member at a positionspaced axially from said flange means, the outer periphery defined bysaid shoulder means being greater in diameter than said washer aperturewhereby to prevent unauthorized axial separation of the washer and saidretainer member, said washer retainer member at a position spacedaxially from said flange means formed inwardly to present a diametermeasurement less than the crest diameter of the threads of said screwmember, said inwardly formed portions being laterally yieldable topermit telescopic association with said screw member, said tubularretainer member after being mounted on said screw member being laterallyyieldable to permit telescopic association of the apertured washerwhereby to provide an electrically insulated washer relative to thescrew member with which it is associated.
 2. A fastener unit as setforth in claim 1, wherein the shoulder means comprises a radiallyoutwardly deflected annular portion of said tubular retainer member. 3.A fastener unit as set forth in claim 1, wherein the tubular retainermember has an internal diameter which progressively decreases toward theentering extremity of the screw member associated therewith.
 4. Afastener unit as set forth in claim 1, wherein the screw member has anunthreaded shank portion adjacent the clamping surface of the head.
 5. Afastener unit as set forth in claim 1, wherein the inner margin of thewasher member defining the washer aperture is of substantially reducedaxial thickness.
 6. A fastener unit as set forth in claim 1, wherein theinner margin of the washer member defining the washer apertureprogressively diminishes radially inwardly to provide a marginal edgefor engaging the outer periphery of the tubular retainer member.
 7. Afastener unit as set forth in claim 1, wherein the outer margin of saidwasher member being provided with teeth for aggressively impinging saidwork surface.